1. Field of the Invention
The present invention relates to a medical instrument whose distal end is inserted into a body cavity of a subject when it is used and to a valve adapted to be fitted over a mount piece of the medical instrument.
2. Description of the Related Art
A technique using a tube insertion guide unit is known which is employed to introduce a catheter for a contrast medium into a body cavity such as a blood vessel. For example, the Published Unexamined Japanese Patent Application 59-133877 discloses a valve which is fitted on the open end of the tube guide unit. The valve is used to prevent an external flow of blood via an internal passage of the guide unit.
Such a valve is required even in a simple catheter so as to prevent an external flow of a fluid.
In an endoscope, a channel tube is used to inject a liquid medicine into the body cavity of a patient or to insert a distal end of a treating instrument, to for example, resect or pick up an affected or diseased region of the patient. During the use of the endoscope, a valve is served to prevent an external leakage of a gas or wastes in the body cavity through the channel tube due to a change in an internal pressure prevalent in the body cavity. The Published Unexamined Japanese Patent Application 62-275447, for example, discloses a sealing valve which is mounted on the opened end of a channel tube of the endoscope.
The valve is made of an elastic material such as rubber and includes a closed film having a slit. A treating unit, such as forceps or catheter, is inserted through the slit of the closed film of the valve into the channel tube. Upon the insertion of the treating unit in this way, the valve seals the inside of the channel against the external endoscope.
In the aforementioned conventional valve assembly, an annular groove provided in the inner wall surface of the valve is fitted over a flange provided on a mounting seat of a mounting mount piece, or a projection provided on the outer periphery of the valve is fitted into an associated annular groove on the inner surface of a mounting mount piece, or the valve is attached by a proper mounting member to the mount piece. The valve can be removed from the associated mount piece by a reversed process without destroying it.
Since, in this way, the valve is attached to and detached from the associated mount piece without destroying it or impairing its function, even if the valve is soiled by a body fluid or partially broken upon the insertion and withdrawal of the treating unit into and away from the channel tube, there is a risk that it will be reused without being aware of these facts.
In the case where the valve has an uneven surface necessary for attachment or detachment to and from an associated mount piece, it is difficult to completely wash away the wastes from the uneven surface of the valve.
In order to avoid a possible risk of a human subject developing an infection or to achieve the accuracy with which a region of interest of the subject is picked up for examination, it is absolutely necessary to replace a "once-used" valve with a new one after a medical examination has been performed.
A valid countermeasure is, therefore, required so that the once-used valve is inadvertently not reused for medical treatment.